NANDFLASH management method based on FAT file system

[0026] Example 1

[0027] Such as figure 1 As shown, a NANDFLASH management method based on the FAT file system is to first detect each block in the NANDFLASH, find the bad block, then process the bad block, convert the physical address of the bad block into a cluster number, and finally The cluster number of the bad block is marked in the FAT table; the value of the mark must be greater than the largest cluster number in the FAT table, so that the mark value does not overlap with the valid cluster number, and in this case, it will always be written to the file. Will not write to this cluster.

[0028] The physical address of the bad block is converted into a cluster number by the bad block processing program, and the converted code is:

[0029] for(i=0; i

[0030] {

[0031] BadClusNum[i]=BadBlkNum*ClusPerBlk+2;

[0032] }

[0033] Among them, ClusPerBlk represents the number of clusters per block; BadClusNum represents the cluster number corresponding to the bad block; BadBlkNum represents the address of the bad block, and +2 is because the cluster number in the FAT table starts from 2. Assuming that each block of a piece of NANDFLASH has 4 clusters (the specific number of clusters in each block needs to be determined by the computer according to the capacity of NANDFLASH, here is just an assumption), if the second block is detected as a bad block, then according to the above conversion code We know that the cluster numbers corresponding to this block are clusters 10, 11, 12, and 13; finally, mark the position corresponding to the cluster number in the FAT table, and update the FAT table after the marking is completed.

[0034] The detection is to erase the block first. When the erase block is unsuccessful, it means that it is a bad block. When the erase is successful, data is written to the block, and then the written data is read out and the original data is compared. The difference between the two indicates that the block is a bad block.

[0035] Below is a part of a typical FAT table.

[0036] offset

[0037] F8 FF FF FF is the start mark of the FAT table.

[0038] 00 00 indicates a free cluster.

[0039] FF FF is the end of file mark.

[0040] For example, if you want to read a file, suppose its starting cluster is the 5th cluster, the content of the 5th cluster on the FAT table is 0800, then it will reach the 8th cluster, the 8th cluster is 0C00, and then it will reach the 12th cluster. Cluster, the content of the 12th cluster is FFFF, which means that the last data of this file is less than one cluster, and reading the file ends here (that is, the data of this file is located on the 5th, 8th, and 12th clusters). If we want to write a file, first look for a free directory in the root directory area, and then query the free cluster on the FAT table (query the free flag 0000), and erase the physical block corresponding to the cluster after finding it. If the erasing fails, the cluster corresponding to the block is marked with FE FF to indicate that it is not available. Otherwise, write data to this cluster, and then read it after writing, and then perform data error correction, if the data after error correction If the data is different from the original data, the cluster corresponding to the block is marked with FE FF to indicate that it is not available. After marking, continue to search for free clusters until the file is written, and then update the FAT table.

[0041] Example 2

[0042] When the NANDFLASH is formatted, the computer will calculate the relevant information according to the FLASH capacity and put it into the DBR. FAT divides the FLASH space according to a certain number of sectors, each sector is 512Bytes, and multiple sectors form a " cluster". The following structure is the detailed information in DBR:

[0043] #define UINT8 unsigned char

[0044] #define UINT16 unsigned int

[0045] #define UINT32 unsigned long

[0046] typedef struct

[0047] {

[0048] UINT8 jmpBoot[3]; /*Jump instruction */

[0049] UINT8 OEMName[8]; /*vendor name */

[0050] UINT16 BytsPerSec; /*Bytes per sector */

[0051] UINT8 SecPerClus; /*Number of sectors per cluster */

[0052] UINT16 RsvdSecCnt; /*Number of reserved sectors */

[0053] UINT8 NumFATs; /*Number of FAT tables */

[0054] UINT16 RootEntCnt; /*Maximum number of root directory files, 0 in FAT32 */

[0055] UINT16 TotSec16; /*Total number of sectors, 0 in FAT32 */

[0056] UINT8 Media; /*Media descriptor */

[0057] UINT16 FATSz16; /*Number of sectors per FAT */

[0058] UINT16 SecPerTrk; /*Number of sectors per track */

[0059] UINT16 NumHeads; /*Number of heads (number of sides) */

[0060] UINT32 HiddSec; /*The number of hidden sectors */

[0061] UINT32 TotSec32; /*If BPB_TotSec16=0, record the total number of sectors */

[0062] UINT8 DrvNum; /*drive of interrupt 13 */

[0063] UINT8 Reserved1; /*Reserved */

[0064] UINT8 BootSig; /*Extended boot flag */

[0065] UINT32 VolID; /*Volume serial number */

[0066] UINT8 VolLab[11]; /*Volume label */

[0067] UINT8 FilSysType[8]; /*File system type */

[0068] UINT8 Code[448]; /*boot code */

[0069] UINT16 Over; /*End flag */

[0070] }DBRINFO;

[0071] Take Samsung K9K8G08U1M as an example. It has 4096 blocks, each block contains 64 pages, and each page is composed of 4 sectors and a 64-byte spare area. The total size is 512M+16M (16M is spare area). The following is the DBR area information of the FAT file system established on this block of NANDFLASH.

[0072] 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

[0073] 01: EB 3C 90 4D 53 57 49 4E 34 2E 31 00 02 10 01 00

[0074] 02: 02 00 02 00 00 F8 F9 00 20 00 3E 00 20 00 00 00

[0075] 03: 00 86 0F 00 80 00 29 22 96 1B 00 61 61 61 00 00

[0076] 04: 00 00 00 00 00 00 46 41 54 31 36 20 20 20 FA 33

[0077] 05: C0 8E D0 BC 00 7C 16 07 BB 78 00 36 C5 37 1E 56

[0078] 06: 16 53 BF 3E 7C B9 0B 00 FC F3 A4 06 1F C6 45 FE

[0079] 07: 0F 8B 0E 18 7C 88 4D F9 89 47 02 C7 07 3E 7C FB

[0080] 08: CD 13 72 79 33 C0 39 06 13 7C 74 08 8B 0E 13 7C

[0081] 09: 89 0E 20 7C A0 10 7C F7 26 16 7C 03 06 1C 7C 13

[0082] 10: 16 1E 7C 03 06 0E 7C 83 D2 00 A3 50 7C 89 16 52

[0083] 11: 7C A3 49 7C 89 16 4B 7C B8 20 00 F7 26 11 7C 8B

[0084] 12: 1E 0B 7C 03 C3 48 F7 F3 01 06 49 7C 83 16 4B 7C

[0085] 13:00 BB 00 05 8B 16 52 7C A1 50 7C E8 92 00 72 1D

[0086] 14: B0 01 E8 AC 00 72 16 8B FB B9 0B 00 BE E6 7D F3

[0087] 15: A6 75 0A 8D 7F 20 B9 0B 00 F3 A6 74 18 BE 9E 7D

[0088] 16: E8 5F 00 33 C0 CD 16 5E 1F 8F 04 8F 44 02 CD 19

[0089] 17: 58 58 58 EB E8 8B 47 1A 48 48 8A 1E 0D 7C 32 FF

[0090] 18: F7 E3 03 06 49 7C 13 16 4B 7C BB 00 07 B9 03 00

[0091] 19: 50 52 51 E8 3A 00 72 D8 B0 01 E8 54 00 59 5A 58

[0092] 20: 72 BB 05 01 00 83 D2 00 03 1E 0B 7C E2 E2 8A 2E

[0093] 21:15 7C 8A 16 24 7C 8B 1E 49 7C A1 4B 7C EA 00 00

[0094] 22: 70 00 AC 0A C0 74 29 B4 0E BB 07 00 CD 10 EB F2

[0095] 23: 3B 16 18 7C 73 19 F7 36 18 7C FE C2 88 16 4F 7C

[0096] 24: 33 D2 F7 36 1A 7C 88 16 25 7C A3 4D 7C F8 C3 F9

[0097] 25: C3 B4 02 8B 16 4D 7C B1 06 D2 E6 0A 36 4F 7C 8B

[0098] 26: CA 86 E9 8A 16 24 7C 8A 36 25 7C CD 13 C3 0D 0A

[0099] 27: 4E 6F 6E 2D 53 79 73 74 65 6D 20 64 69 73 6B 20

[0100] 28: 6F 72 20 64 69 73 6B 20 65 72 72 6F 72 0D 0A 52

[0101] 29: 65 70 6C 61 63 65 20 61 6E 64 20 70 72 65 73 73

[0102] 30: 20 61 6E 79 20 6B 65 79 20 77 68 65 6E 20 72 65

[0103] 31: 61 64 79 0D 0A 00 49 4F 20 20 20 20 20 20 53 59

[0104] 32: 53 4D 53 44 4F 53 20 20 2053 59 53 00 00 55 AA

[0105] The underlined part in the above table is the BPB information of 53 bytes. From the table, you can know:

[0106] Number of bytes per sector: BytesPerSector = 0x0200;

[0107] The number of sectors per cluster: SecPerClus=0x10;

[0108] The total number of sectors: TotSec32=0xF8600;

[0109] Since SecPerBlock=256.

[0110] So the number of clusters per block can be calculated:

[0111] ClusPerBlock=SecPerBlock/SecPerClus=16.

[0112] The following table is a sector of the FAT table after bad block processing (bad block mark has been made in the table):

[0113] 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

[0114] 01: F8 FF FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00

[0115] 02: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0116] 03: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0117] 04: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0118] 05: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0119] 06:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0120] 07: 00 00 00 00 FE FF FE FF FE FF FE FF FE FF FE FF

[0121] 08: FE FF FE FF FE FF FE FF FE FF FE FF FE FF FE FF

[0122] 09: FE FF FE FF 00 00 00 00 00 00 00 00 00 00 00 00 00

[0123] 10:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0124] 11:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0125] 12: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0126] 13:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0127] 14:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0128] 15:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0129] 16:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0130] 17:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0131] 18:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0132] 19:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0133] 20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0134] 21: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0135] 22:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0136] 23:00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0137] 24: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0138] 25: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0139] 26: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0140] 27: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0141] 28: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0142] 29: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0143] 30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0144] 31: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

[0145] 32: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00